The objectives are to develop low-risk an high-risk diets that will produce, respectively, relatively small amounts of slightly degraded fecal steroids and relatively high levels of highly degraded fecal steroids. Further studies will be made to relate these conditions to the incidence of colon cancer by determining the effects of these diets on the activity of selected fecal and intestinal mucosa enzymes that could be involved in colon carcinogenesis. The effects of these diets on the induction of cancer by known colon carcinogens will be studied also.